Connection between two components

ABSTRACT

A method of connecting a fixture to a case component at an opening on the case component, the case component having a base and a wall disposed along at least a portion of the perimeter of the base, and the case component having an interior surface and an exterior surface, includes positioning a first end of the fixture within the opening in the case component such that the first end of the fixture is substantially flush with the interior surface of the wall of the case component. Then welding the fixture to the case component along the interior surface of the case component. Further disclosed is a welded apparatus that includes a first component, an opening, a fixture, and a weld between the first component and the fixture that is located along an inner surface of the first component.

BACKGROUND OF THE INVENTION

It is often desired to connect components using welding to fabricate ahermetically sealed connection. Medical devices, including encapsulatedIMDs, frequently comprise a case structure (or similar component) andone or more fixtures, such as fillports for liquid electrolyte,electrical feedthroughs (e.g., multipolar and single-pin feedthroughs),ferrules, sensors, needles, nozzles, electrical connectors, and similarcomponents, that establish electrical communication through the casewith a hermetic seal.

Implantable medical devices (IMDs) include pacemakers, cardioverters,defibrillators, and other devices for therapeutic stimulation of theheart, as well as other devices such as implantable devices foradministering drugs. Such devices can include a flat electrolyticcapacitor (FEC), a wet valve metal-slug capacitor (e.g., a high energywet tantalum capacitor), a primary battery, a secondary battery, a drugpump, an infusion pump and the like. An example is the IMD set forth inU.S. Pat. No. 6,118,652 entitled “Implantable Medical Device Having FlatElectrolytic Capacitor With Laser Welded Cover.”

In one application, one or more FEC stores energy required fordefibrillation therapy deliver to the myocardium of a subject. An FECtypically includes an electrode assembly having an anode structure, acathode, a separator (or spacer), an electrolyte (which can function asthe cathode), and a case for enclosing the capacitor and containing theelectrolyte. The capacitor stores energy in an electric field generatedby opposing electrical charges on either side of an oxide layer formedon the anode. The energy stored is proportional to the surface area ofthe anode. The oxide layer is generally formed during electrolysis,where electrical current is passed through the anode.

Tabs or terminals can extend outside the case for electricallyconnecting the capacitor to external objects (e.g., to electrode coilsdisposed in electrical communication with myocardial tissue of asubject). Feedthroughs can be used to fabricate electrical or otherconnections that extend through the FEC case.

A fillport is typically connected to the capacitor case duringfabrication. The fillport permits a fluid, namely the electrolyte, to beintroduced into the case at an appropriate stage during fabrication.Once the capacitor has been filled with electrolyte, the fillport can becut or trimmed close to the case and then capped as part of a process ofsealing the electrolyte within the capacitor. The capacitor utilizeshermetic seals for preventing fluids from the capacitor from leaking,which is impermissible when the medical device is implanted in a hostbody. In addition, hermetic seals help assure proper function of thecapacitor and the medical device by limiting contamination andpreventing necessary fluids from draining.

Known manufacturing processes for attaching two components with ahermetic seal present a number of problems and limitations. Typicallywhen manufacturing medical devices, according to those known methods,fixtures such as fillports are placed at an opening on the case,generally protruding outward from the case. A flange on the fillportrests along an outer surface of the case and a sealing or connectionportion of the fillport is situated within the opening. The fillport istypically temporarily held in place at the opening by gravity or avacuum. The fillport and case are then welded together by forming aweld, often a laser weld, between the flange of the fillport and theexterior surface of the case. This weld resembles a lap joint. Weldsformed between the flange on the fillport and the exterior of the caseoften exhibit poor weld penetration. The weld must penetrate three oxidelayers, which are located on the flange of the fixture (i.e., top andbottom surfaces of the flange) and the exterior surface of the case.Welding though oxide layers is difficult.

In addition, these welds leave small gaps or crevices between thefillport and the case between the weld (on the exterior surface of thecase) and an interior surface of the case. Stress points are formed atsuch gaps or crevices, which can result in poor weld and seal integrity.This can lead to a broken seal and also a broken connection, which arecollectively referred to as weld failures. Furthermore, when the casecontains a fluid, for example when the case is part of a FEC containingan electrolyte, fluid can collect within gaps and crevices between thefillport and the case (between the weld and the interior surface of thecase), which causes processing issues, crevice corrosion, andexacerbates undesirable stresses at such locations.

Moreover, the fixture can become misaligned during manufacturing,leading to an improper connection and/or seal. With known manufacturingprocesses it is difficult to clamp or otherwise secure fixtures to acase component while welding. This makes it difficult to deal withmisalignment problems.

Further, manufacturing process are generally limited to manipulating alaser beam or other welding means from a position relative to theexterior surface of the case. In some instances the laser beaminadvertently impinges upon a portion of a component to be welded (e.g.,an elongated fillport tube protruding toward the laser source) thusreducing yield and increasing scrap and costs related thereto.

Thus a more reliable sealed connection between two components, and amethod of forming such a connection, is needed.

BRIEF SUMMARY OF THE INVENTION

The present invention generally relates to a method of connecting afixture to a case component at an opening on the case component, thecase component having a base and a wall disposed along at least aportion of the perimeter of the base, and the case component having aninterior surface and an exterior surface. A first end of the fixture ispositioned within the opening in the case component such that the firstend of the fixture is substantially flush with the interior surface ofthe wall of the case component. The fixture is then welded to the casecomponent along the interior surface of the case component.

Further, a welded device includes a first component having an opening, afixture, and a weld. The first component includes a base and a side walldisposed on the base. The first component defines an inner surface andan outer surface. The fixture includes an axial shaft, a radiallyextending flange adjacent to the axial shaft and an connection portiondistal to the radially extending flange. The connection portion of thefixture is positioned within the opening in the first component and theflange is disposed adjacent the outer surface of the first component.The weld is located between the first component and the connectionportion of the fixture at the inner surface of the first component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a block diagram of a laser welding system.

FIG. 2 depicts a perspective view of a case component.

FIG. 3 depicts a cross-sectional view of a fillport.

FIG. 4 depicts a perspective view of a cross-sectional portion of anassembly including a case component and a fillport.

FIG. 5 depicts a cross-sectional elevation view of a portion of theassembly of FIG. 4.

FIG. 6 depicts a perspective view of the assembly and a portion of alaser welding system.

FIG. 7 depicts a cross-sectional view of a welded assembly.

FIG. 8 depicts a bottom elevational view of the welded assembly of FIG.7.

FIG. 9A depicts a perspective view of a jig and side elevation view ofsaid jig, respectively.

FIG. 9B is a perspective view of the jig of FIG. 9A and components to bewelded.

FIG. 10 is a perspective view of another jig.

FIG. 11 is a perspective view of a pallet.

FIG. 12 is a perspective view of the pallet of FIG. 11 and a number ofjigs.

FIG. 13 is a perspective view of a base plate.

FIG. 14 is an illustration of an ellipse.

DETAILED DESCRIPTION

The present invention relates to a connection between two components anda method of making such a connection. More particularly, the presentinvention relates to connecting two components, such as components of anIMD, by forming a hermetic seal with a weld.

FIG. 1 is a block diagram of a laser welding system 30. The laserwelding system 30 can include a laser 32, a shutter 34, a vision system36, a gas supply 38, a nozzle 40, and a motion controller 42. One ormore jigs 44 can be placed on a pallet 46, which in turn can be placedon a base plate 48. Components C_(w) placed on the one or more jigs 44can thereby be engaged by the laser welding system 30. It should benoted, however, that the laser welding system 30 shown and describedwith respect to FIG. 1 is one example, and other welding systems can beutilized according to the present invention.

The laser 32 is capable of generating laser beams, which can applyenergy to a particular area for melting materials to form hermeticwelds. The laser 32 can generate one or more discreet laser beams (e.g.,by controlling laser pulses through current sent to the laser's 32 flashlamps) as pulses of energy, and the pulses are adjustable in pulse width(i.e., duration), pulse rate (i.e., frequency), and pulse height (i.e.,beam intensity). The shutter 34 is a safety mechanism that can block alllaser beams generated by the laser 32. Typically the shutter 34 has anon/off configuration, where the shutter 34 is either entirely open orentirely closed.

The vision system 36 optically senses characteristics of componentsC_(w) engaged with the laser welding system 30. For example, the visionsystem 36 can be a pixel-based system that is capable of taking a“snapshot” of a portion of a component to weld C_(w) and analyzing,inter alia, a geometry and position of features of that component C_(w)based upon pixels of the “snapshot.” A weld path can be determined usinginput and feedback from the vision system 36. The vision system 36 andthe laser 32 can be focused together on a particular portion of thecomponent to be welded C_(w).

The gas supply 38 allows a cover gas, typically an inert gas like argon,helium and combinations of those elements, to be supplied when the laser32 is forming a weld. Laser welding can generate oxides and soot thatcan rise off of welding path as a laser beam melts material on acomponent being welded C_(w). Supplying a gas can reduce generation ofparticulate matter (oxides and soots), as well as reduce associatedcontamination. The gas can be supplied with an appropriate flow force tohelp dissipate a “cloud” of particulate matter generated during welding,as desired. The particular gas selected will vary according tocharacteristics of a particular application (e.g., according to materialproperties of the components to be welded C_(w)).

The laser 32, the vision system 34, and the gas supply 36 can all berouted through the nozzle 40. Typically the nozzle 40 is hollow and canbe generally cone-shaped. A tip of the nozzle 40 is positioned in closeproximity to components to be welded C_(w). Generally, the nozzle 40will be positioned to allow suitable clearance spacing between thenozzle 40 and the components to be welded C_(w), such that the nozzle 40does not physically contact the components to be welded C_(w) despiteany relative movements during welding. Physical contact can producemisalignment between the laser 32 and the components to be welded C_(w).

As noted, gas can be supplied through the nozzle 40 co-axially with thelaser beam from the laser 32. In further embodiments, gas can besupplied at different orientations, such as from an auxiliary locationoutside the nozzle 40 applying gas sideways (i.e., radially with respectto the nozzle 40). A desired orientation of supplied gas will varyaccording to characteristics of particular applications. For instance, ageometry of components to be welded C_(w) can influence selection andprovision of a more desirable gas supply.

The motion controller 42 permits X, Y and Z direction movement of baseplate 48, and in turn, movement of the components to be welded C_(w).Using the motion controller 42, relative movement of the laser 32 andthe components to be welded C_(w) can be initiated for positioning alaser beam from the laser 32 at a desired location on the components tobe welded C_(w) to make a weld.

FIG. 2 is a perspective view of a case component 54, which in thisexample is part of a flat electrolytic capacitor (FEC) case. In theembodiment shown in FIG. 2, the case component 54 includes a base 56 anda number of walls 58, 60, 62 and 64. A fillport opening 66 is disposedin the wall 58 of the case component 54. A first opening 68 and a secondopening 70 are disposed in the wall 62.

The walls 58, 60, 62 and 64 are disposed at a perimeter of the base 56.Typically the walls 58, 60, 62 and 64 are arranged to extend from thebase 56 in an orientation substantially perpendicular to the base 56,though other arrangements are possible. The base 56 and walls 58, 60, 62and 64 form an open cavity therebetween. An interior surface 72 of thecase 54 is defined along that cavity. An exterior surface 74 is furtherdefined on the case 54, opposite the interior surface 72.

The case component 54 is typically made of aluminum, stainless steel, ortitanium, but can be any laser-weldable material. Fixtures such as suchas fillports, feedthroughs (e.g., multipolar and single-pinfeedthroughs), ferrules, sensors, needles, nozzles, electricalconnectors, and similar components can be connected to the casecomponent 54 at any of the openings 66, 68 and 70.

The openings 66, 68, and 70 each have a generally circular shape, thoughother shapes are possible. The openings 66, 68, and 70 are typicallypositioned along the walls 58, 60, 62, and 64 of the case component 54and extend through an entire thickness of material forming the casecomponent 54. In further embodiments, the openings 66, 68, and 70 arepositioned elsewhere on the case component 54.

FIG. 3 is a cross-sectional view of a fillport 78, which includes anaxial shaft portion 80, a radially-extending flange portion 82, aconnection portion 84, and an inner opening 86. The radially-extendingflange portion 82 is adjacent to the axial shaft portion 80, and theconnection portion 84 is located adjacent to the radially-extendingflange portion 82 distal to the axial shaft portion 80. The inneropening 86 extends through the entire fillport 78, thereby defining afluid path through the fillport 78. The fillport 78 can comprise anylaser-weldable material, such as aluminum, stainless steel, titanium andother metals. In alterative embodiments, the fillport 78 can be asubstantially straight tube without a flange. FIG. 4 is a perspectiveview of a cross-sectional portion of an assembly 90 including a casecomponent 54 and a fillport 78, and prior to welding. As shown in FIG.4, the assembly 90 has not yet been welded. The fillport 78 ispositioned at an opening 66 in a wall 58 of the case component 54. Aconnection portion 84 of the fillport 78 is positioned within theopening 66 such that the connection portion 84 of the fillport 78 issubstantially flush with an interior surface 72 of the case component54. A radially-extending flange portion 82 of the fillport 78 ispositioned adjacent an exterior surface 74 of the case component 54. Anaxial shaft portion 80 of the fillport 78 projects outward from theexterior surface 74 of the case component 54. An inner opening 86 of thefillport 78 is in fluid communication with a cavity defined by the casecomponent 54.

FIG. 5 is a cross-sectional elevation view of a portion of the assembly90 prior to welding. As shown in FIG. 5, a connection region 92 isdefined where the fillport 78 and the case component 54 meet (i.e., at ajoint area at a perimeter of the opening 66).

FIG. 6 is a perspective view of the assembly 90 and a portion of a laserwelding system 30 that includes a nozzle 40. The nozzle 40 is positionedin close proximity to the interior surface 72 of the case component 54.The laser welding system 30 generates a laser beam L_(B) that can,according to a weld schedule, move along a weld path defined at or nearthe connection region 92 between the fillport 78 and the case component54.

FIG. 7 is a cross-sectional view of a welded assembly 90W, whichcorresponds to the unwelded assembly 90 shown and described with respectto FIGS. 4-6 after welding. As shown in FIG. 7, a weld 94 is disposedbetween the fillport 78 and the case component 54. The weld 94 extendsfrom the interior surface 72 of the case component 54. A connection ismade by the weld 94 that generally resembles a butt joint. A weldpenetration depth (i.e., a distance the weld 94 extends from theinterior surface 72) can vary. It is generally desired to increase theweld penetration depth without penetrating beyond a thickness ofavailable material. For example, establishing a weld with penetrationdepth sufficient to extend into the radially-extending flange portion 82of the fillport 78 without causing damage exterior portions of theradially-extending flange portion 82.

FIG. 8 depicts a bottom elevational view of the welded assembly 90W. Asshown in FIG. 8, the weld 94 can comprise a plurality of discretewelding events (i.e., laser beam pulses) that collectively form the weld94 in a substantially circular shape. In further embodiments, the weld94 can be formed continuously. In one form of the invention, the weld 94surrounds a pierceable septum (not depicted), which would be disposed onthe interior of the fillport 78 portion so that the weld 94 hermeticallyseals a fluid-containing reservoir one interior surface of which wouldcomprise case component 54. The septum is used to manually refill a drugreservoir of an implantable drum pump or infusion device, or the like.The septum can be formed of a variety of polymer or resin-basedmaterials. Such materials preferably self-heal when a syringe tip iswithdrawn.

The weld 94, shown in FIGS. 7 and 8, provides a sealed connectionbetween the fillport 78 and the case component 54. That seal can be ahermetic seal. The weld 94 can further be formed such that no gaps orcrevices are formed where the fillport 78 and the case component 54 areconnected (i.e., on the interior of a hemetically-sealed liquid-filledcase).

FIG. 9A is a perspective view of a first embodiment of a jig 44A, whichincludes a support structure 100A, a repositionable structure 102A,positioning means 104A for positioning the repositionable structure 102Arelative to the support structure 100A, biasing means 106A for biasingthe repositionable structure 102A for securing items to the jig 44A, andfixture holder 108A. The jig 44A can be used with the laser weldingsystem 30 for holding and securing components to be welded (e.g., theassembly 90 of FIGS. 4-5).

In the embodiment shown in FIG. 9A, the biasing means 106A is a coiledspring assembly that can bias the repositionable structure 102A in adirection toward the fixture holder 108A. At least a portion of afixture, such as a fillport (e.g., the fillport 78 shown in FIG. 3), canbe placed in the fixture holder 108A. An item, such as a case componentfor a FEC (e.g., the case component 54 shown in FIG. 2), can bepositioned between the support structure 100A and the repositionablestructure 102A. The repositionable structure 102A can be moved along thepositioning means 104A, which can be a mechanical slide that permitsonly linear movement. Where an item is positioned between the supportstructure 100A and the repositionable structure 102A, and a fixture ispositioned in the fixture holder 108A, the biasing means 106A generallyprovides a biasing force to more affirmatively engage the item and thefixture for welding, with a decreased risk of misalignment.

FIG. 9B is a perspective view of the of jig 44A with an assembly ofcomponents to be welded C_(w1) and C_(w2) engaged thereto. ComponentC_(w2) is disposed substantially within the fixture holder 108A, andcomponent C_(w1) is disposed between the repositionable structure 102Aand the support structure 100A. As shown in FIG. 9B, the components tobe welded C_(w1) and C_(w2) are biased against each other. Such biasingfacilitates forming a connection weld between the components to bewelded C_(w1) and C_(w2).

FIG. 10 is a perspective view of another embodiment of a jig 44B, whichincludes a support structure 100B, a repositionable structure 102B,positioning means 104B for positioning the repositionable structure 102Brelative to the support structure 10B, biasing means 106B for biasingthe repositionable structure 102B for securing items to the jig 44B, andfixture holders 108B, 110B, and 112B. In the embodiment shown in FIG.10, the biasing means 106B comprises a magnetic assembly, where magnetsprovide a biasing force for biasing the repositionable structure 102B ina direction toward either the fixture holder 108B or the fixture holders110B and 112B. The jig 44B generally functions similar to the jig 44Ashown and described with respect to FIG. 9. The jig 44B further permitsone or more additional fixtures to be placed within the fixture holders110B and 112B. The repositionable structure 102B can be moved between afirst position for providing a biasing force toward the fixture holder108B and a second position for providing a biasing force toward thefixture holder 110B and 112B.

The jigs 44A and 44B can be made of metallic, ceramic and polymermaterials, as well as combinations of those materials. It will berecognized that other embodiments of jigs may be used other than theexemplary jigs shown and described. For example, in lieu of magneticbiasing means, metallic springs, resin-based resilient members, linearactuators, so-called stepper motors, electrical servo-motors, mechanicaldetents (interlocking structures) and the like can equally serve for thepurposes of alignment and retention.

FIG. 11 is a perspective view of a pallet 120, which includes one ormore engagement surfaces 122, 124 and 126, a plurality of jig engagementmeans 128, and base plate attachment means. The engagement surfaces 122,124 and 126 are generally disposed at an angle (e.g., 20°). Jigs arepositioned at an angle on the engagement surfaces 122, 124 and 126.Items secures in the jigs are likewise disposed at an angle, whichenables better positioning of a nozzle of a laser welding system inclose proximity to components to weld while still permitting adequateclearance to avoid physical contact with the nozzle. The plurality ofjig engagement means 128, such as notched pegs or other means, permitone or more jigs to be quickly and securely engages to associated holesor other engagement means on a pallet.

FIG. 12 is a perspective view of the pallet 120 with a number of jigs44A engaged thereto. Alternatively, in further embodiments, the pallet120 can have a substantially flat upper engagement surface and jigsengaged thereon can incorporate a titled or angled portion forpositioning components to be welded at an angle relative to a nozzle ofa laser welding system. In other words, the jigs and/or the pallet canbe used to position the components to be welded relative to a weldingsystem.

In one embodiment, the base plate attachment means 130 includes one ormore magnets disposed along an exterior portion of the pallet 120, suchas along a perimeter of the pallet 120. Those magnets can be used toprovide an affirmative engagement of a pallet with other components of awelding system. This allows, for example, the pallet 120 to bemagnetically aligned within the laser welding system 30 shown anddescribed with respect to FIG. 1.

FIG. 13 depicts a perspective view of a base plate 48, which includes abase 138, and a pair of stops 140 and 142. A pallet (e.g., the pallet120 shown in FIGS. 11-12) can be positioned on the base 138 of the baseplate 48 and rest against the pair of stops 140 and 142. Base plateattachment means on the pallet can be used to affirmatively engage thebase plate and to reduce a risk of misalignment therebetween. The baseplate 48 can comprise a metallic material for engaging magnets of theattachment means 130 of the pallet 120. In one embodiment, the baseplate 48 is connected to a platen 144 for engaging the base plate withina welding system, for example, engaging the base plate to a stage withina laser welding system.

The base plate 48 can be moved in at least X- and Y- (i.e., lateral) andoptionally Z-directions within a welding system by a motion controller.Movement of the base plate 48 allows movement of items and componentssecured thereto, which enables relative movements to be made between alaser beam and components to be welded that are indirectly secured tothe base plate 48.

In operation, a substantially circular weld (e.g., the weld 94 shown inFIG. 8) is formed on welded components that are disposed at an angle bypositioning welding means along a generally elliptical three-dimensionalweld path to form that weld. Forming generally circular welds alongexterior portions of welded components is relatively simple, because thewelding means can be positioned perpendicular to a connection regionwhere the weld is to be made and there are few problems withobstructions or clearance. It becomes necessary to utilize such anelliptical weld path where the weld is located on an interior portion ofthe welded components and, during welding, the welding means cannot bedisposed perpendicular to a connection region due to inadequateclearance. In such situations the components to be welded C_(w) musttypically be tilted (at an angle other than 90[ ]) relative to thewelding means. Tilting in that manner means that relative movementsbetween the welding means and the components to be welded C_(w) will notdirectly correspond to a desire shape of the complete weld. Statedanother way, the weld path will have a different shape than that of thecompleted weld.

According to the present invention, and with reference to embodimentsshown in FIGS. 1-13, a vision system 36 is used to optically sense aconnection region between an assembly of at least two components to bewelded C_(w) (e.g., a case component 54 and a fillport 78) and capturean image. Then a substantially elliptical path is determined in athree-dimensional space based on the image from the vision system 36.Then a relative movement is initiated between the assembly C_(w) and thewelding means (e.g., a laser beam L_(B) from a laser welding system 30)such that the welding means is positioned, by relative movement, alongthe substantially elliptical path to produce a weld between the firstcomponent and the second component according to a weld schedule.

The vision system 36 (within the welding system 30) is generallyoriented vertically, while components to be welded C_(w) may be tiltedat an angle (i.e., not disposed perpendicular to an orientation of thevision system 36). A substantially circular region to be welded thusappears as a two-dimensional ellipse to the vision system 36.

FIG. 14 is an illustration of an ellipse, shown in two dimensions. Theellipse has a center C, a semimajor axis a, and a semiminor axis b. Aline with a length r′ is defined between the center C and a point (x, y)on the ellipse. An eccentric angle θ′, measured from the center C of theellipse, is defined between the line having length r′ and the semimajoraxis a. An eccentricity e of the ellipse, where 0 e<1, is a constantdefined as: $e \equiv \sqrt{1 - \frac{b^{2}}{a^{2}}}$

A first embodiment of a method of forming a substantially circular weldis as follows. Initially, the vision system 36 locates the center (C) ofa substantially elliptical three-dimensional weld path in X, Y, ZCartesian coordinates, a length of a semimajor axis (a), and a length ofa semiminor axis (b). The center (C) can be located automatically (i.e.,by generally positioning the vision system near a desired weld path andusing the vision system 36 to automatically determine the center), ormanual location of a welding path can occur (i.e., cross hairs of thevision system 36 can be manually aligned at two or more points along thewelding path, and the center determined from those points). Where apixel-based vision system is utilized, data is generally converted toinches, or some other unit of measure, for commanding operation of thewelding system 30. The weld path can be determined by dynamicallydetecting a connection region between components to be welded togetherC_(w) (e.g., at a joint area) in order to establish the ellipseparameters: the center (C), the length of the semimajor axis (a), andthe length of the semiminor axis (b). As a calibrating step for thelaser welding system 30, a “test shot” laser beam can be fired with thelaser welding system 30 and that “test shot” compared with a location ofthe center of the elliptical path (C), with relative positioning of thelaser welding system 30 then adjusted accordingly to reach the startingpoint. Moreover, offset constants can be utilized to adjust thesemimajor and semiminor axes (a and b) of the weld path as determined bythe vision system. Such offset adjustments are used to orient a centerof the weld with a radial spacing from a connection region detectable bythe vision system (e.g., radially offset from a joint area betweencomponents to be welded together C_(w)).

Using information determined by the vision system 36, the welding system30 determines a pattern of discreet weld points along the substantiallyelliptical three-dimensional weld path. In order to accomplish that,calculations are made using to determine two-dimensional characteristicsof the weld path (i.e., X and Y dimension characteristics of the weldpath). A first angular increment (θ′) from the center (C′) of thesubstantially elliptical weld path is established, in polar coordinates.The angular increment can be, for example, three degrees (3°). A firstradial length (r′) at the first angular increment (θ′) is determinedbetween the center (C′) and the ellipse itself. The first radial length(r′) is determined by the following equation:$r^{\prime} = \sqrt{\frac{a^{2}\left( {1 - e^{2}} \right)}{1 - {e^{2}\quad\cos^{2\quad}\quad\theta^{\prime}}}}$

A first point (x, y) along the substantially elliptical weld pathcorresponding to where the first radial length (r′) intersects theellipse at the first angular increment (θ′) is then determined, inCartesian coordinates. The following equations are used to convert polarcoordinates to Cartesian coordinates:x=r′ cos θ′y=r′ sin θ′

Z-dimension locations can be determined, as part of a weld schedule, byassuming the connection region is tilted at a constant angle α (e.g.,20°) in only one direction (e.g., a slope only in the Y direction). Suchan assumption is practical where appropriately standardized tooling isused. A Z-dimension location z for a given point on a substantiallyelliptical three-dimensional weld path is given by the followingequation:z=y tan α

A point on a weld path, such as the first point on the weld path, canthus be located in a three-dimensional Cartesian coordinate system.

Additional points (i.e., a second point, third point, etc.) on the weldpath are generally established by adding angular increments anddetermining associated coordinates in a manner similar to that describedabove. This is an incremental process that determines three-dimensionalcoordinate locations for each discreet point along a substantiallyelliptical three-dimensional weld path.

Next, the welding system 30 is positioned, by relative movement betweenthe welding system 30 and the components to be welded C_(w), at astarting point on the substantially elliptical three-dimensional path(e.g., a point where the semimajor axis intersects the ellipse in FIG.14) such that energy (i.e., the laser beam L_(B) in a laser weldingsystem 30) can be directed at that point. A relative movement betweenthe welding means (i.e., the laser beam L_(B) in the laser weldingsystem 30) and the substantially elliptical three-dimensional path isinitiated for positioning welding means (i.e., the laser beam L_(B) inthe laser welding system 30) at the first point (x, y, z) along thesubstantially elliptical three-dimensional path. While motion of a stagein a laser welding system 30 may only physically occur in X and Ydirection, Z-dimension adjustments can be accomplished using laser focusadjustment and/or z-dimension stage motion, as needed and desired.

The welding means (i.e., a laser beam L_(B) in a laser welding system30) can then be repositioned relative to any number of additional pointsalong the weld path. The welding means is incrementally repositionedrelative to each discreet point established along the weld path andapplies energy to each of those points. Energy from the welding meansmelts material of the components to be welded C_(w), which form a weldedconnection. The weld path can be a closed polygon (or polyhedron),defined by individual points along the weld path, for forming a sealwith the welded connection. The weld path can also have other closedshapes, such as closed shapes including curvilinear portions.

In one embodiment, pulse height of a laser beam L_(B) used with a laserwelding system 30 is ramped-up during early stages of a weld schedule.Ramping-up pulse height means that pulse height (i.e., laser beamintensity) increases over a period of time. The ramp-up can includeopening a shutter 34 on the laser welding system 30 and firing laserbeam pulses at components to be welded C_(w) before the pulse height issufficiently great to melt material on the components to be weldedC_(w), and the increasing the pulse height to a magnitude sufficient tomelt material for welding. In addition, pulse height can be ramped-downnear completion of a weld schedule. Ramping-down is generally describedas the reverse of a ramping-up process.

Typically in embodiments where ramping-up (and/or ramping-down)techniques are used, the laser welding system 30 completes at least onefull “trip” or “revolution” along a weld path with the laser beam L_(B)firing at full pulse height (i.e., at an intensity sufficient to meltmaterial of the component to be welded C_(w)). Further, a weld schedulecan include positioning the laser beam L_(B) over portions of a weldpath already traversed. For example, the laser beam L_(B) can bepositioned to fire laser pulses along a weld path for two or morecomplete “trips” or “revolutions.” Those skilled in the art willrecognize that a particular weld schedule will vary according tocharacteristics of a particular application, and use of ramping-up(and/or ramping-down) will vary according to other characteristics of aweld schedule, including pulse width, pulse height, and pulse rate.

In further embodiments, the laser beam L_(B) of the laser welding system30 is used only at full pulse height in a binary on/off manner. Theshutter 34 can be used to accomplish such on/off operation of the lasersystem 30.

Thus, according to the present invention two components are connectedtogether with a weld that forms a seal. This invention has manyapplications, including making sealed connections for medical devices,including encapsulated IMDs. Such medical devices frequently comprise acase structure (or similar component) and one or more fixtures, such asfillports, feedthroughs (e.g., multipolar and single-pin feedthroughs),ferrules, sensors, needles, nozzles, electrical connectors, and similarcomponents, that are connected to the case with a hermetic seal, whichcan be made according to the present invention.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. For example, while the foregoing descriptionof the substantially elliptical three-dimensional weld path refers tothe laser welding system 30 of FIG. 1, it will be recognized that otherwelding means and other configurations of a welding system can be usedaccording the present invention. For example, the present invention canbe used to fabricate any liquid-filled electrochemical cell (e.g.,primary or secondary batter, aluminum FEC capacitor, wet-slug capacitorhaving a valve metal anode, etc.) or other implantable device thatbenefits from hermetically sealed case and/or fluid reservoir (e.g., animplantable drug pump, infusion pump, etc.). With respect to drug orinfusion pumps, the invention can advantageously weld the perimeter of aferrule surrounding a septum through which a liquid therapeutic agent isperiodically injected.

1. A method of connecting a fixture to a case component at an opening on the case component, the case component having a base and a wall disposed along at least a portion of the perimeter of the base, and the case component having an interior surface and an exterior surface, the method comprising: positioning a first end of the fixture within the opening in the case component such that the first end of the fixture is substantially flush with the interior surface of the wall of the case component; and welding the fixture to the case component along the interior surface of the case component.
 2. A method according to claim 1 and further comprising: biasing the fixture against the case component prior to welding.
 3. A method according to claim 1, wherein the opening is disposed in the wall of the case component.
 4. A method according to claim 1, wherein the wall is positioned substantially perpendicular to the base.
 5. A method according to claim 1, wherein the fixture includes an inner opening extending through the fixture.
 6. A method according to claim 1, wherein a hermetic seal is formed by the weld between the fixture and the case component at the inner surface of the case component.
 7. A method according to claim 1, wherein the opening comprises a substantially circular configuration.
 8. A method according to claim 1, wherein a laser welds the fixture to the case component.
 9. A welded apparatus comprising: a first component having a base and a side wall disposed on the base, wherein the first component defines an inner surface and an outer surface; an opening defined in the first component; a fixture having an axial shaft, a radially extending flange adjacent to the axial shaft and an connection portion distal to the radially extending flange, wherein the connection portion of the fixture is positioned within the opening in the first component and the flange is disposed adjacent the outer surface of the first component; and a weld between the first component and the connection portion of the fixture at the inner surface of the first component.
 10. A welded apparatus according to claim 9, wherein the opening is disposed in the side wall of the first component.
 11. A welded apparatus according to claim 9, wherein the side wall is positioned substantially perpendicular to the base.
 12. A welded apparatus according to claim 9, wherein the fixture includes an inner opening extending through the entire fixture.
 13. A welded apparatus according to claim 9, wherein the weld forms a hermetic seal between the connection portion of the fixture and first component.
 14. A welded apparatus according to claim 9, wherein the opening is substantially circular.
 15. An apparatus for a medical device, the apparatus comprising: a case component having a base and a plurality of walls disposed along a perimeter of the base, wherein the case component includes an interior face and an exterior face, the walls disposed substantially perpendicular to the base of the case component; an opening disposed in one of the walls of the case component; and a fixture attached to the case component at the opening by a weld made along the interior face of the case component for hermetically sealing the fixture to the case component.
 16. An apparatus according to claim 15, wherein an inner opening is defined through the fixture.
 17. An apparatus according to claim 15, wherein the weld includes a substantially circular shape.
 18. An apparatus according to claim 15, wherein the weld is a laser weld.
 19. An apparatus according to claim 15, wherein the fixture is a fillport.
 20. An apparatus according to claim 15, wherein the fixture is a ferrule.
 21. A fluid containment apparatus comprising: a case including an interior surface and an exterior surface and an opening extending therebetween; and a fixture connected to the case at the opening, wherein the fixture is connected to the case by a weld located at the interior surface of the case, and wherein the fixture includes a flange disposed adjacent to the exterior surface of the case.
 22. A fluid containment apparatus according to claim 21, wherein a portion of the fixture extends substantially outward from the exterior surface of the case.
 23. A fluid containment apparatus according to claim 21, wherein the weld forms a hermetic seal between the case and the fixture.
 24. A medium for encoding instructions for performing a welding method to produce a hermetic joint surrounding a component to an adjacent surface, comprising: instructions for optically sensing a connection region between the first component and the second component to produce an image; instructions for defining a substantially elliptical path in a three-dimensional space based on the image; and instructions for initiating relative movement between the assembly and welding means such that the welding means is positioned, by relative movement, along the substantially elliptical path to produce a weld between the first component and the second component.
 25. A medium according to claim 24, wherein the weld defines a continuous hermetic path in one plane and further comprises a substantially planar, circular shape. 